The present invention relates to the screening and detecting of blood disorders and more particularly to the screening and detecting of common thalassaemias and especially beta thalassaemia minor.
Currently in the United States many people are being offered education, testing, and genetic counselling for variant haemoglobins. It soon may be obligatory in the United States for physicians to inform patients of genetic risks, in which case, tests for variant haemoglobins should be able to screen detect thalassaemias and in particular beta thalassaemia minor.
The thalassaemias are a group of clinically important disorders caused by inherited defects in the rate of synthesis of normal haemoglobin. Beta thalassaemia minor is the most common of the thalassaemias and is the heterozygous expression of one of a set of genes, one of which produces no haemoglobin A, one of which interacts with beta chain variants producing a considerable amount of haemoglobin A but produces no increase in the RBC, and one of which has no haematological or clinical manifestations.
In the homozygous state, beta thalassaemia causes the death of about one hundred thousand children in the world per annum. It is thus desirable for there to be an accurate, yet relatively simple and inexpensive means to screen and detect the carriers of thalassaemias. As for any autosomal recessive disorder, theoretically the incidence of the homozygote could be reduced almost to zero if the heterozygote could be detected. An ideal test for the detection of heterozygotes should have no false negatives, few false positives and should be simple and reliable. Several tests in the past have been used, including measurement of osmotic fragility, fetal haemoblobin, free red cell porphyrin, blood smears, and haemoglobin A.sub.2, yet none is readily adapted to mass screening. With the advent of electronic particle counters, estimates of red cell indices became more attractive and were combined or used singly to identify heterozygotes. As set forth herein, the three best methods were tested on 25,302 samples and all were found to miss known heterozygotes.